Variation In Egg Shape Research Articles

Egg shape variation across the distribution of the partially migratory fork‐tailed flycatcher Tyrannus savana

The evolution of egg shape across birds has been associated with breeding ecology, body shape constraints and nest microclimate, among other factors. We model the effects of migratory status, climate, clutch size and egg volume on egg shape variation over the distribution of fork‐tailed flycatchers Tyrannus savana. Although migratory status and climatic variables appear to be influencing intraspecific egg shape, these effects are not significant when accounting for nest identity as a random factor (i.e. eggs from the same clutch are more similar than to other clutches). Moreover, the differences that we observe in egg shape are not explained by variation in egg size. Finally, within a breeding population of migratory fork‐tailed flycatchers, egg shape does not vary with respect to egg‐laying order and/or female wing length (standardized by weight). Egg shape is highly variable within populations of fork‐tailed flycatchers but not within clutches, suggesting that female traits, apart from migratory status and wing morphology, constrain egg shape variation.

Allometry of Egg Size as a Factor Influencing Egg Shape in Birds

Despite a huge diversity of egg shapes among birds, similar egg shapes occur in species that differ in habitats and are not phylogenetically closely related; this indicates the presence of factors limiting the egg shape variability. We assume that one of these factors is a general pattern of egg shape change across all birds. We tested a hypothesis of allometric patterns of egg morphometric traits (radii of blunt end (infundibular zone, ri), pointed end (cloacal zone, rc), lateral zone (rl) and maximum diameter (D)) scaling against egg length (L). Phylogenetic allometric analysis was applied. We also studied hierarchical distribution of variation in egg traits at different taxonomic levels in order to determine the degree of egg shape variability on each of them. We revealed allometric patterns in the scaling of egg traits: D and ri scaled against L with negative allometry, while rc and rl were positively allometric. A high degree of covariation was observed between the length and diameter, radii of the lateral and infundibular zones, i.e. traits that are associated with the overall size of an egg, the degree of its elongation, and the shape of infundibular zone. Evolutionary correlation between L and rc was rather low. The greatest variation of egg traits resided at the level of orders. The identified general trends in egg shape variation are realized on the basis of various groups of birds in phylogenetic and ecological sense that assume the influence of these factors on the bird's egg shape.

Effects of the Lung Volume on the Electroglottographic Waveform in Trained Female Singers

ObjectivesTo determine if in singing there is an effect of lung volume on the electroglottographic waveform, and if so, how it varies over the voice range. Study designEight trained female singers sang the tune “Frère Jacques” in 18 conditions: three phonetic contexts, three dynamic levels, and high or low lung volume. Conditions were randomized and replicated. MethodsThe audio and EGG signals were recorded in synchrony with signals tracking respiration and vertical larynx position. The first 10 Fourier descriptors of every EGG cycle were computed. These spectral data were clustered statistically, and the clusters were mapped by color into a voice range profile display, thus visualizing the EGG waveform changes under the influence of fo and SPL. The rank correlations and effect sizes of the relationships between relative lung volume and several adduction-related EGG wave shape metrics were similarly rendered on a color scale, in voice range profile-style ʻvoice maps.ʼ ResultsIn most subjects, EGG waveforms varied considerably over the voice range. Within subjects, reproducibility was high, not only across the replications, but also across the phonetic contexts. The EGG waveforms were quite individual, as was the nature of the EGG shape variation across the range. EGG metrics were significantly correlated to changes in lung volume, in parts of the range of the song, and in most subjects. However, the effect sizes of the relative lung volume were generally much smaller than the effects of fo and SPL, and the relationships always varied, even changing polarity from one part of the range to another. ConclusionsMost subjects exhibited small, reproducible effects of the relative lung volume on the EGG waveform. Some hypothesized influences of tracheal pull were seen, mostly at the lowest SPLs. The effects were however highly variable, both across the moderately wide fo-SPL range and across subjects. Different singers may be applying different techniques and compensatory behaviors with changing lung volume. The outcomes emphasize the importance of making observations over a substantial part of the voice range, and not only of phonations sustained at a few fundamental frequencies and sound levels.

A consistent long-lasting pattern of spatial variation in egg size and shape in blue tits (Cyanistes caeruleus)

BackgroundInterspecies variation in avian egg shape and size is understandable in terms of adaptation, allometry and phylogeny. Within-species variation in egg properties influences offspring fitness and can be explained by differences in allocation of resources into reproductive components of life history in mulidimensionally variable environments. Egg size is inherently traded-off with clutch size, which may also be true of egg shape in some cases. We investigated long-term variation in egg shape and size between two geographically close populations of blue tits Cyanistes caeruleus in relation to clutch size and habitat differences.ResultsThe main finding is that there exists a persistent long-lasting pattern of spatial variation of egg size and shape between the two study populations of blue tits, 10 km apart, controlling for clutch size. Eggs in the urban park site were on average larger in volume and less spherical in shape than eggs in the forest site over 12 years of this study. Egg sizes were negatively associated with clutch sizes. Egg shape was not correlated with clutch size.ConclusionsOur findings suggest that the pattern of variation in egg size and shape results from different trophic richness of the breeding habitats of the study populations, demanding different allocation of resources and, especially, from the contrasting difference in the availability of calcium.

A new, three-dimensional geometric morphometric approach to assess egg shape.

This paper proposes a new methodology to quantify patterns of egg shape variation using geometric morphometrics of three-dimensional landmarks captured on digitally reconstructed eggshells and demonstrates its performance in capturing shape variation at multiple biological levels. This methodology offers unique benefits to complement established linear measurement or two-dimensional (2D) contour profiling techniques by (i) providing a more precise representation of eggshell curvature by accounting for variation across the entire surface of the egg; (ii) avoids the occurrence of correlations from combining multiple egg shape features; (iii) avoids error stemming from projecting a highly-curved three-dimensional (3D) object into 2D space; and (iv) enables integration into 3D workflows such as finite elements analysis. To demonstrate, we quantify patterns of egg shape variation and estimate morphological disparity at multiple biological levels, within and between clutches and among species of four passerine species of different lineages, using volumetric dataset obtained from micro computed tomography. The results indicate that species broadly have differently shaped eggs, but with extensive within-species variation so that all four-focal species occupy a range of shapes. Within-species variation is attributed to between-clutch differences in egg shape; within-clutch variation is surprisingly substantial. Recent comparative analyses that aim to explain shape variation among avian taxa have largely ignored potential biases due to within-species variation, or use methods limited to a narrow range of egg shapes. Through our approach, we suggest that there is appreciable variation in egg shape across clutches and that this variation needs to be accounted for in future research. The approach developed in this study to assess variation in shape is freely accessible and can be applied to any spherical-to-conical shaped object, including eggs of non-avian dinosaurs and reptiles through to other extant taxa such as poultry.

Effect of composition on shape of bird eggs

Numerous studies over the past 90 years have described the various bird egg shapes in mathematical terms but few studies have considered the underlying reasons for such interspecific egg shape variability. This study investigated how the size and composition, i.e. proportions of shell, yolk and albumen, were associated with egg shape. Geometric morphometrics were used to generate principal components, which were analysed in relation to taxonomy (i.e. avian order) and degree of neonatal developmental maturity, which correlates with egg composition. The analysis confirmed previous results that most of the variation in shape is associated with degree of elongation (i.e. length divided by breadth) and asymmetry (i.e. position of the broadest part of the egg away from the mid‐point of the egg's length). Egg shape reflected avian order but not developmental maturity. The degree of elongation of an egg is related to absolute egg mass and the proportion of yolk. By contrast, the degree of asymmetry is related to the proportion of shell and the mass of the egg relative to female body mass. Although significant, the models explained little of the variation in egg shape and so it was concluded that other factors, such as pelvis size and shape, could be more important in determining egg shape in birds.

Egg shape in the Common Guillemot Uria aalge and Brunnich\u2019s Guillemot U. lomvia: not a rolling matter?

The adaptive significance of avian egg shape is poorly understood, and has been studied only in those species producing pyriform (pear-shaped, or pointed) eggs: waders and guillemots (murres) Uria spp., albeit to a limited extent. In the latter, it is widely believed that the pyriform shape has evolved to minimise their likelihood of rolling off a cliff ledge: the idea being that the more pointed the egg, the narrower the arc in which it rolls, and the less likely it is it will fall from a cliff ledge. Previous research also claimed that the rolling trajectory—the diameter of the arc they describe—of Common Guillemot U. aalge eggs is influenced not only by its shape but also by its mass, with heavier (i.e. larger) eggs describing a wider arc than lighter eggs. The finding that both shape and mass determined the rolling trajectory of Common Guillemot eggs (the shape–mass hypothesis) was used to explain the apparent anomaly that Brünnich’s Guillemot U. lomvia produce eggs that are less pointed, yet breed on narrower ledges than Common Guillemots. They are able to do this, it was suggested, because Brünnich’s Guillemot eggs are smaller and lighter in mass than those of Common Guillemots. However, since some populations of Brünnich’s Guillemots produce eggs that are as large or larger than those of some Common Guillemot populations, the shape–mass hypothesis predicts that that (1) larger (i.e. heavier) eggs of both guillemot species will be more pyriform (pointed) in shape, and (2) that eggs of the two species of same mass should be similarly pointed. We tested these predictions and found: (1) only a weak, positive association between egg volume and pointedness in both guillemot species (<3% of the variation in egg shape explained by egg volume), and (2) no evidence that eggs of the two species of similar mass were more similar in shape: regardless of their mass, Brunnich’s Guillemot eggs were less pointed than Common Guillemot eggs. Overall, our results call into question the long-held belief that protection from rolling is the main selective factor driving guillemot egg shape.

A simple tool for calculating egg shape, volume and surface area from digital images

The geometrical properties of eggs – such as volume and surface area – have uses ranging from ecological, physiological and morphological studies in birds, to predictions of chick condition in the poultry industry. Although measurements of an egg's length and breadth can be used to approximate its geometry, the coefficients used in these models are specific to the original test population, and intraspecific variation in egg shape means these methods cannot be used reliably beyond that population. Here I present a novel mathematical formula to describe the curvature of a bird's egg that can be used to calculate the shape, volume and surface area of an egg precisely from digital images. Using data from several species I demonstrate that the model has a greater level of accuracy than length‐ and breadth‐based methods, and release the user‐friendly tool for others to use for measuring eggs from digital images.

Salinity and Egg Shape Variation: A Geometric Morphometric Analysis

The harvest and incubation of American Alligator (Alligator mississippiensis) eggs is an important component to the commercial alligator harvest industry in the southeastern United States. As a result, various methodologies have been used to monitor alligator populations including abundance counts, stress quantification, and nesting surveys. Past studies have dismissed the importance of egg shape in crocodilians, Squamates, and turtles and deemed egg shape in birds and other amniotes as similar, in relation to functionality. The complexity of crocodilian eggs has been examined, and both turtle and Squamate eggs have been regarded recently as physiologically more intricate than bird eggs. This study introduces a physiological approach to monitor alligator populations in freshwater and low salinity environments by quantifying egg shape in correlation with varying salinity. We introduce a fractional semilandmark-shape template method to quantify egg shape within a geometric morphometric framework. This approach is beneficial because it allows for the quantification of shape for curved structures, such as eggs, which lack homologous landmarks. The results from this study suggest that alligator egg shape is correlated with varying salinity levels, such that variation in alligator egg shape at low salinities changes in gradient-like fashion, whereas salinities high enough to be deemed stressful result in reversion back to a low salinity egg shape or desiccation. This study elucidates a correlation that can be implemented in management and breeding techniques and opens the door to in-depth physiological examination of the system.

Female condition, egg shape and hatchability: a study on the grey partridge

AbstractEgg features are key components of egg quality that can influence future prospects of survival. Past studies have outlined the importance of egg size, but little is known about egg shape variation, differences among females, influence of external factors on shape and the importance of shape for hatchability. In this study of the grey partridge Perdix perdix, we examined shape characteristics (elongation and three indices derived from photographs). There was a significant individual difference in egg shape among females, and shape was influenced by the position in the laying order, with last‐laid eggs being less elongated. Egg shape indices were not influenced by food quality (experiment with two diets differing in β‐carotene content), nor by an immune challenge (experiment with two groups differing in Newcastle disease virus vaccine treatment). Eggs laid by females in poorer health conditions were more asymmetric and more pointed. Egg hatchability was higher for intermediate egg elongation values.

Calculating egg volume when shape differs: when are equations appropriate?

ABSTRACT Egg volume is often calculated from length and breadth, assuming little variation in egg shape within species. However, egg shape may vary among females, over time, or within clutches. If this variation is not predictable, volume should be estimated using another method. For example, in some species, egg shape changes consistently with laying order and volume can be estimated using laying-order specific equations. We measured the length, breadth, volume, and mass of 249 Magellanic Penguin (Spheniscus magellanicus) eggs and regressed volume on length and breadth for first and second eggs separately. Differences between measured and calculated volume averaged <1% for both eggs. Using linear measurements, we calculated egg volume for 7085 clutches from 1983 to 2006. First and second eggs had similar calculated volumes (P > 0.05) in 19 of 24 yr; when they differed, the second egg was larger. In contrast, using single equations typically employed to compute egg volume, we erroneously concluded that first eggs were usually (20 of 24 yr) significantly larger than second eggs. Our regression equations should be applicable to other Spheniscus penguins because ratios of elongation coefficients (length divided by breadth) of first and second eggs are similar among these species. In other species of birds where egg shape changes with laying order, the volume of a sample of eggs should be measured to develop regression equations specific to the species and laying order. Slight variation in egg volume can have important evolutionary and ecological implications that would be erroneously interpreted without field tests to measure volume. Usualmente el volumen del huevo se calcula basado en el largo y ancho, asumiendo poca variación en la forma del huevo dentro de la especie. Sin embargo, la forma del huevo puede variar entre hembras, a través del tiempo o dentro de la nidada. Si la variación no es predecible, el volumen debería ser estimado con otro método. En algunas especies de aves la forma del huevo cambia consistentemente con el orden de la puesta y el volumen puede ser estimado usando una ecuación específica para el orden de la puesta. Medimos el largo, ancho, volumen y masa en 249 huevos de Spheniscus magellanicus y realizamos una regresión del volumen con el largo y ancho para el primer y segundo huevo por separado. Diferencias entre el volumen medido y calculado promediaron <1% para los dos huevos. Usando medidas lineares, calculamos el volumen del huevo para 7085 nidadas desde 1983 hasta el 2006. El primer y segundo huevo tuvieron volúmenes calculados similares (P > 0.05) en 19 de los 24 años; cuando ocurrieron diferencias el segundo huevo fue más grande. Utilizando una sola ecuación de la literatura para calcular el volumen del huevo obtuvimos conclusiones erróneas en donde el primer huevo (20 de 24 años) fue usualmente significativamente más grande que el segundo huevo. Debido a que las proporciones de los coeficientes de elongación (largo dividido por el ancho) del primer y segundo huevo fueron similares, nuestras ecuacións de la regresión debe ser aplicable a otro pingüinos del genero Spheniscus. En otras especies de aves en donde la forma de los huevos cambian con el orden de la puesta, el volumen de varios huevos debe ser medido para poder obtener una ecuación específica por medio de una regresión, para las especies y el orden de la puesta. Una pequeña variación en el volumen del huevo puede tener implicaciones ecológicas y evolutivas importantes, que pueden ser interpretadas de manera errónea sin medidas previas en el campo del volumen.

A precise water displacement method for estimating egg volume

Relationships between egg volume and an array of life-history traits have been identified for many bird species. Despite the importance of egg volume and the need for precise and accurate measurements, egg volume is usually estimated using a mathematical model that incorporates length and width measurements along with a shape variable. We developed an instrument that provides precise estimates of egg volume and can be easily used in the field. Using Clapper Rail {Rallus longirostris) eggs, we compared egg volumes measured using our instrument with estimates based on linear measurements. We found our instrument to be both precise and accurate. Compared with a method based on linear measurements of eggs, use of our instrument reduced variation in egg volume estimates by 1.6 cm3, approximately 8% of the volume of a Clapper Rail's egg. Further advantages of our technique include ease of use, increased accuracy of field-based volume estimates, and increased resolution of variation in egg volume estimates. In addition, our technique does not require postdata collection processing time and did not influence hatching success. Also, for Clapper Rails and similar species, our technique can be combined with other techniques (e.g., egg flotation) so that both egg volume and embryonic stage can be estimated at the same time.

Measuring egg size using digital photography: testing Hoyt's method using Florida Scrub-Jay eggs

Egg volumes are most often estimated using a mathematical model that incorporates length and width measurements and a species-specific shape variable. Although adequate in many respects, this technique does not account for intraspecific variation in egg shape. We developed a computer-automated technique that uses calibrated digital photographs to render precise measurements of several egg-size parameters including length, width, volume, and surface area. The system extracts egg outlines from photographs, and divides each egg into latitudinal slices that are subsequently regarded as simple geometric shapes (cylinders or cone frustra) with volumes and surface areas that can be summed to generate size parameters for the entire egg. We tested this technique using 491 eggs from Florida Scrub-Jay (Aphelocoma coerulescens) nests and compared the resulting egg volumes with volumes calculated using the preeminent method of estimating volume from linear measurements. Our method was highly accurate, and differences between the volumes from our method and the alternative method were strongly associated with variation in egg shape. Advantages of our technique include decreased handling of eggs and increased accuracy. Software resources and additional information regarding the technique are available at http://www.archbold-station.org/abs/data/birddata/Bridge-JFO-eggsize.htm. SINOPSIS. Medidas de huevos utilizando fotograf´ ia digital: poniendo a pruebas el m´ etodo

The Relationship of Egg Shape to Time of Oviposition and Egg Shell Quality

Experiments were conducted to determine the relationship of egg shape to time of oviposition and egg shell quality. Eggs were collected at 2-hr intervals throughout the day and depending upon the experiment various measurements (egg weight, shape index, shell weight, shell thickness, or specific gravity) were determined.The results indicated that eggs laid during the afternoon had a higher shape index (rounder eggs) than eggs laid during the morning. The afternoon eggs also had a higher specific gravity, shell weight, shell thickness, and were smaller than eggs laid during the morning. A large variation in shape index occurred among eggs.It was concluded that the difference in shape between times of oviposition would not explain the variation in shell quality due to time of oviposition, but that the large variation in egg shape among birds is a significant factor in determining the bird’s ability to produce eggs with maximum shell thickness with a given amount of shell.

Variation in egg shape in Schistosoma haematobium

An account is given of an attempt to define the shape of eggs of Schistosoma haematobium (Bilharz, 1852) (Schistosomatidae; Trematoda), in terms suitable for statistical analysis. The dimensions of over 5,000 eggs from several geographic strains of S. haematobium from Africa and the Middle East obtained from both man and from laboratory infections in hamsters, mice, Mastomys, Arvicanthis, and Meriones are analyzed. The relationships of the various groups are determined by statistical techniques involving the concept of taxonomic distance. Details of the laboratory infections and of the analysis techniques are given, and the results discussed. It is concluded that there is a degree of random variability in egg shape in S. haematobium, but that there is also considerable non-random variability ascribable to different host species and geographic strains.